Purpose <p>In order to analyze the on-site phenomenon that the 20-high rolling mill is prone to vibration when the diameter of the roll system is small, the influence of the elongation of the piston rod and the height of the hydraulic oil column on the vibration characteristics of the 20-high rolling mill was analyzed.</p> Methods <p>Two kinds of simulation limit states are designed, the first is the maximum diameter of the working roll, the first intermediate roll and the second intermediate roll, and the second is the smallest diameter of the working roll, the first intermediate roll and the second intermediate roll. At the same time, the dynamic vibration characteristics of the whole machine were analyzed under these two conditions, considering the elongation of the piston rod of the press-on cylinder and the combination of the elongation of the piston rod of the press-on cylinder and the height of the hydraulic oil column.</p> Results <p>When the elongation of the piston rod of the cylinder is considered alone, the vibration frequency of the rolling mill is abundant, but the vibration amplitude is low. In the context of integrating the elongation of the piston rod from the pressure cylinder with the height of the hydraulic oil column, experimental observations indicate that the rolling mill exhibits a reduced vibration amplitude under the first limit state compared to the second. However, analyses further reveal that both limit states demonstrate a lower frequency concentration and diminished high-frequency vibration amplitudes.</p> Conclusions <p>The research results provide a theoretical reference for further analysis of the influence of hydraulic oil column flow characteristics on rolling mill vibration.</p>